<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Document</title>
    <style>
        *{
            margin: 0px;
            padding: 0px;
        }
        .box{
            display: flex;
            width: 500px;
            height: 450px;
            border: 2px solid red;

            flex-wrap: wrap;

            /* 多根主轴在交叉轴的起点开始排列 */
            /* align-content: flex-start; */

            /* 多根主轴在交叉轴的终点开始排列 */
            /* align-content: flex-end; */

            /* 多根主轴在交叉轴的中点开始排列 */
            /* align-content: center; */

            /* 交叉轴上的富余空间们于两排项目之间 */
            /* align-content: space-between; */

            /* 交叉轴上的富余空间环绕两排项目之间 */
            /* align-content: space-around; */

            align-content: space-evenly;
        }
        .item{
            width: 100px;
            height: 100px;
            text-align: center;
            line-height: 100px;
            border: 2px solid yellowgreen;
        }
    </style>
</head>
<body>
    <!-- 容器 -->
    <div class="box">
        <!-- 项目 -->
        <div class="item">one</div>
        <div class="item">two</div>
        <div class="item">three</div>
        <div class="item">four</div>
        <div class="item">five</div>
        <div class="item">six</div>
        <div class="item">seven</div>
        <div class="item">eight</div>
    </div>
</body>
</html>